This invention relates to an improved process for the conversion of p-nitrobenzal bromide to p-nitrobenzotribromide. p-NItrobenzotribromide is an intermediate to the insecticide, 1,5-bis(4-trifluoromethylphenyl)-3-cyanoformazan which is described in the German publication Offenlegungsschrift 2,460,255.
H. Fisher in Journal of American Chemical Society, 56, 2469 (1934) reports the conversion of p-nitrobenzal bromide to p-nitrobenzotribromide by reacting p-nitrobenzal bromide in a heterogeneous aqueous reaction medium with sodium hypobromite at 25.degree. C for four days, which results in a 78% yield. R. G. Jones in Journal of American Chemical Society, 69, 2346 (1947) reports the same conversion on a larger scale according to the method of Fisher, but with a two-fold excess of sodium hypobromite.
Maginmity and Eisenmann in Journal of American Chemical Society, 74, 6119 (1952), Fukui in Nippon Kagaku Zasshi, 79, 899 (1958) [ Chemical Abstract 54, 4430 (1958)] and South African Patent 68-06,020 (1969) also mention the preparation of p-nitrobenzotribromide from p-nitrobenzal bromide in an aqueous sodium hypobromite system.